A large number of different types of telecommunications and data networks for communicating and/or transmitting data are known. A distinction can be drawn here between two fundamentally different types of network. There are, on the one hand, the telecommunications networks, for example those conforming to the GSM (Global System for Mobile Telecommunications) or the UMTS (Universal Mobile Telecommunications System) standards, in which subscribers are authenticated and authorized when they sign on to the network concerned. An advantage in networks of this type is that as a result of the authentication procedure it is also possible to charge for services used. Furthermore, these generally cellular networks offer the opportunity of a high degree of mobility since a subscriber can move with his/her station from network cell to network cell. A disadvantage of these types of cellular telecommunications systems is that the administrative outlay is very high. Also, these telecommunications networks provide only a low data rate for radio interfaces.
There are, on the other hand, data networks which are designed as local area networks or wireless local area networks (WLAN). Such data networks offer subscriber stations access that is very easy to administer. A further advantage consists in the considerably higher data rate by comparison with telecommunications networks at the interfaces to the subscriber station. A disadvantage of data networks of this type, however, is the lack of an authentication facility and consequently also the lack of a billing or charging facility.
Currently, especially in the USA and Europe, it is almost exclusively products based on the IEEE 802.11 family which appear to be prevailing as local area networks with wireless subscriber access, with suitable Ethernet terminals already being provided as standard in many computers and portable computers (laptops, notebooks, PDAs, etc.). The radio interface defined under the IEEE 802.11b standard for accessing local area networks corresponds functionally to a wired connection to LANs which have now developed into the office standard. Interface cards for wireless access to local area networks, also referred to as NICs (network interface cards), are from an architectural point of view produced like standardized Ethernet cards and with today's operating systems can be installed using plug & play. Portable computers are readily upgradeable with appropriate interface cards unless they have already been delivered ex works with an integrated terminal for wired or wireless access to local area networks. With the next generations of operating systems (e.g. Windows XP from Microsoft) fully integrated support for wireless local area networks will be provided.
With data rates of 11 Mbit/s at present and of 50 Mbit/s in future, subscribers will thus be provided with data rates that are considerably higher than the data rates which can be offered by the next third-generation mobile telecommunications (UMTS). Access to wireless local area networks for high-bit-rate connections is consequently preferable for transmitting large quantities of data, especially in connection with Internet access.
Disadvantageously, the wireless local area networks cannot offer any authentication facility for stations or computers not already registered in the system. However, operators of wireless local area networks, for example in an airport area, have to offer access for a large number of different subscribers from different regions. In order to be able to authenticate a subscriber, the operator of the wireless local area network would have to conclude cross-license agreements with all possible Internet service providers (ISPs), of which, however, there are currently over 60,000 in Germany alone.
Without authenticating subscribers or subscribers' stations, no billing of services used can occur since it is not even known to whom a bill could be sent. Access to wireless local area networks must therefore either be offered free of charge or as a prepaid service with payment in advance by means of credit card billing or the like.
A further facility enabling authentication and billing consists in involving a billing company or clearing house which takes responsibility for the relevant contacts with as many Internet service providers worldwide as possible. A problem here, however, is that a large proportion of the revenues of the operator of a wireless local area network has to be transferred to the clearing house. Furthermore, the clearing house has to succeed in being able to contact each actual Internet service provider or at least a large number of Internet service providers, i.e. in concluding a large number of contracts itself. This solution, too, is consequently very difficult to manage. With regard to unauthorized access to data networks there is also increasingly the problem that unauthenticated content is being provided by subscribers of wireless local area networks. Only authentication could prevent extremist information or information that jeopardizes young people from being retrieved via the local area networks concerned and via access to the Internet.
These problems can be solved by the operators of the mobile communications networks in a simple way. The cellular mobile communications networks have a large subscriber base that can be authenticated. Furthermore, these mobile communications networks have an accounting or billing system. By means of international roaming, subscribers who are registered or subscribed with another mobile communications network operator can also be serviced and authenticated. Since nowadays a majority of consumers in industrialized countries are mobile telephone subscribers, a mobile communications network operator can in principle contact virtually every consumer itself or with the aid of other mobile communications network operators.
Initiatives as to how a mobile communications network operator can integrated wireless local area network into its own cellular mobile communications network are many and various. As the debate stands at present, a distinction is drawn between tight and loose coupling. Tight coupling is defined as full UMTS integration, i.e. one uses only the physical layer of the wireless local area network, while all higher protocol layers are taken over from UMTS and adapted. This solution is meanwhile no longer under discussion as it has proven not to make economic sense and to be technically difficult to implement.
Among the variants of loose coupling currently being debated publicly are the two infrastructure-based coupling variants (e.g. ETSI BRAN) which are based on the use of a registered identification card (SIM: subscriber identification module) or the RADIUS PROTOCOL (RADIUS: Remote Access Dial-In User Access). In the case of the SIM-based variant, a SIM card is installed in a notebook or a network access card for said notebook. The wireless local area network system appears logically as a visitor local register (VLR) of the telecommunications network and is connected to the telecommunications network via the MAP (mobile application part). Economic success for the operator of the telecommunications network depends greatly, however, on whether in future every card for accessing wireless local area networks will contain a SIM card as standard. For this to occur, computer manufacturers and the standardization bodies for data networks and telecommunications networks would have to develop joint standards or a mobile communications network operator would have to subsidize this specific type of NIC.
In the case of the RADIUS variant, the telecommunications network appears as an authentication, authorization and accounting server, as a result of which no modification of subscriber equipment is necessary.
With regard to currently available hardware, access points (AP) which are based on the IEEE 802.11b standard are known, as analog modems for connecting to a telephone line, as ISDN cards for connecting to an So bus, as DSL modems for connecting to a DSL line, topologically as Ethernet bridges with a local area network terminal for connecting to a local area network and in further embodiments as a cable modem for connecting to a cable television network and as a router, for example with an Ethernet terminal without a bridge function. These access points consist of a radio access section for controlling access to the radio interface and an interface for connecting to the wired telecommunications or data network. The radio access section and the interface for the line-bound terminal are connected with hardware which also provides appropriate configuration management functions, etc.